Create a standby server

Hello,
I have a master and tow standby servers. I want to create another one. These servers are made by someone else and I am
anewbie in PostgreSQL. 
I found the following two tutorials:

https://linuxconfig.org/how-to-create-a-hot-standby-with-postgresql

https://github.com/GoogleCloudPlatform/community/blob/master/archived/setting-up-postgres-hot-standby.md

A) Which on is better and easier?

B) In these articles, to create a Standby server, a user is created in the database. Because there are already two
Standbyservers, this user is probably created. How can I find it? Can I use that user to build a third server? 


Cheers.